Receiving system in a superheterodyne radio receiver



p 1963 SUEKlCHl rro ETAL 3,103,631

RECEIVING SYSTEM IN A SUPERHETERODYNE RADIO RECEIVER v Filed March 6,1961 3 Sheets-Sheet. 1

P 1-963 SUEKICHI lTO-ETAL 3,103,631

RECEIVING SYSTEM IN A SUPERHETERODYNE RADIO RECEIVER Filed March 6, 19613 Sheets-Sheet 3 WNW United States Patent This invention relates tosuperheterodyne type radio receivers, and more particularly it relatesto a new receiving system utilizing, together, crystal oscillation andself-oscillation for local oscillation in a superheterodyne type radioreceiver.

It is an object of the invention to provide a receiving 2 systemwherein, in the case of receiving broadcasts and other communicationsignals by means of a superhetero dyne receiver, by inserting a crystaloscillator of predetermined trequency in a local oscillation circuit, itis possible to adjust easily and, at the same time, to receive stably aspecial radio wave, and it is possible also to receive other frequenciesby self-oscillation in the same manner as in the ordinary case.

It is another object of the invention to provide a novel crystaloscillator composed of two or more crystals, which is capable ofproducing two or more crystal oscillations, and which is suitable forsuch uses as that in the receiving system according to the invention. I

The manner in which the foregoing as well as other objects andadvantages of the present invention, as will become apparent presently,may best -be achieved will be understood more fully irorn :aconsideration of the fol lowing description, taken in conjunction withthe accompanying illustrations in which the same and equivalent partsare designated by the same reference letters or numerals, and in which:2

FIG. 1 is a circuit diagram of a converter of an ordinary two-handsuperheterodyne receiver;

FIGS. 2 to 6 are circuit diagrams showing different local oscillatorcircuits of a superheterodyne receiver according to the presentinvention;

FIGS. 7 to 9 are circuit diagrams showing difierent local oscillatorcircuits of a transistor type superhete-rodyne receiver according to thepresentinvention;

FIG. 10 is a circuit diagram wherein a crystal oscillator is connectedin parallel to the local oscillator coil of a so-called NSB tuner, i.e.,a device capable of receiving short waves by the addition of componentsfor intermediate wave use;

FIG. 11 is a plan view showing one representative embodiment of acrystal oscillator with three crystal pieces inserted in one holder;

FIG. 12 is a sectioned view along the lines l2--12 of FIG. 11;

FIGS. 13 through 15 are connection diagrams of three crystal pieces intheoscillator illustrated in FIGS. 11 and 12, and show, respectively,the cases wherein three crystal pieces are connected in series, inparallel, and one crystal is connected in series to a parallelconnection consisting of two crystals; and

FIG. 16 is a connection diagram of four crystal pieces of another emhodiment of this application.

The ordinary two-band superheterodyne receiver of FIG. 1 comprises afrequency converting vacuurntube V a high frequency tuning condenser C alocal oscillator variable condenser C said condensers C and C beingganged, semi-fixed trimer-condensers C C C and C =a semi-fixed paddingcondenser O; for intermediate trequency =b-and local oscillator, asemi-fixed padding condenser C 'for short wave band'local oscillation, agrid condenser C for local oscillation, a high tre- Patented Sept. 10,19 63 quency tuning coil L for intermediate frequency wave band, a highfrequency tuning coil L for short wave band, a local oscillator coil Lfor intermediate frequency band, a local oscillator coil L, for shortwave band, a grid resistance R for local oscillation, an intermediatefrequency transformer T and band changing switches 8 -8 which are alsoganged.

In the local oscillator circuits shown in FIGS. 2 to 6 which are to heused in the superheterodyne receiver of this invention, the same membersas those of the circuit of FIG. 1 are designated by the same referencecharacters except the vacuum tube V for the local oscillat tion and thecrystal oscillator X. In the circuit of FIG.

2, the crystal oscillator X is connected in series to the oscillatorgrid condenser C in the circuit of FIG. 3, the crystal oscillator X isused instead of the oscillator grid condenser C in the circuit of FIG.4, the crystal oscillator X is connected between the oscillator gridandground; in the circuit of FIG. 5, the crystal oscillator X is connectedin parallel to the oscillator variable condenser; and in the circuit ofFIG. 6, the crystal oscillator X is connected between the cathode of theoscillator vacuum tube V and ground.

In the local. oscillator circuits shown in FIGS. 7, 8, and 9 which areto be used in the transistor type superheterodyne receiver according tothe present invention, the reference characters TR X, L,,, C C C and Ldesignate, respectively, a local oscillator transistor, a crystaloscillator, a local oscillation coil, a variable condenser for localoscillation, semi-fixed padding condenser for local oscillation, afeed-back condenser, and an oscilia-tor coupling coil. I

In the circuit of FIG. 7, the crystal oscillator X is connected in thefeedback circuit of the local oscillator circuit; in the circuit of FIG.8, the crystal oscillator is connected to the feed-back circuit of thebase feedback type local cscillator circuit; and in the circuit of FIG.9, the crystal oscillator X is connected in parallel in the localoscillator condenser C The circuit of FIG. 10, in which the crystaloscillator X is connected in parallel to the local oscillator coil ofthe NSB tuner, comprises a high irequency tuning coil L a localoscillation coil L and intermediate treqnencyshort 'wave changingswitches S and S which are in ganged state.

In the circuits of FIGS. 11 to 16, the crystal pieces are designated bynumerals 1, 2, 3, and 4; electrode plates are designated by numerals 5,6, 7 and 8; and electrodes and holder are designated, respectively, by 9land 10, and 11.

In a two-band, superheterodyne receiver of ordinary type for broadcastreception, the adjustment of the variable condenser for reception in theshortwave band (high-frequency band) is extremely difiicult, even aslight detuning being suirlcient to prevent reception of the intendedradio wave. Moreover, even if appropriate adjustment is attained whenthe use of the receiver is initially begun, the frequency of the localoscillation varies with time because of the variation of temperaturewithin the receiver; consequently, detuning results, and it becomesimpossible to receive the desired radio wave.

The above-described disadvantage can be eliminated, and stable receptionobtained by the system of the present invention. For example, in thecase of receiving a radio wave of 3,925 kc, if the intermediatefrequency of the receiver is made to be 455 kc, a crystal oscillator Xof 3,925 kc.+455kc.=4,380 kc, frequency is inserted as indicated inFIGS. 2 through 9, inclusively, in one of the positions indicated as A,B, and C in FIG. 1, and the receiver is thus adjusted, the crystaloscillator will oscillate at its natural frequency when the naturalfrequency of the L,C C circuit of FIG. 1 approaches 4,380

3 r kc., and it will be possible to receive, easily, a radio Wavef3,9'25 kc.

In this case, even if the capacitance of the condenser is variedslightly, the frequency of the crystal oscillation will undergo almostno change. ceiving condition is extremely stable, and even when thetemperature Within the receiver or the voltage of the 1 power sourcevaries after a long period of reception, al-

most no detuning occurs.

Furthermore, while the conventional receiver of ordinary type often hasthe disadvantage of radio interference by waves of frequencies in theproximity of the desired frequency because of poor adjustment, thesystem of the present invention maintains the receiver constantly in theoptimum adjustment condition for reception with,

an ordinary receiver, and, accordingly, the degree of radio interferenceby proximate Waves is extremely low.

It'is common practice in the reception of shortwaves to use radio wavesof two or more frequencies because of the nature of shortwavepropagation and to receive by selecting the frequency which is mostsuitable depending on the time and season.

Accordingly, the rc- In such a case, therefore, if two or more crystaloscillators which have frequencies Since, in this case it is possible toreceive .thedesired radio wave well and in astable manner over anextremely wide range of rotational angle of the tuning dial as comparedto the case of ordinary reception, if the system, is utilized forreception in the high-frequency band, adjustment will be extremely easy.

I When the system of the present invention is to be used to receiveradio waves of frequencies other than the orig-.

inally intended frequency with the crystal oscillator still inserted,reception is possible in this condition through self-oscillation.Accordingly, when the system is applied to an all-wave'receiver,excellent performance is obtained.

Furthermore, when the system of the invention is applied to a five-tubesuperheterodyne receiver (medium wave) and used simply for an NSB tunerwhich becomes a two-band receiver, if the above-mentioned crystaloscillator is inserted in parallel with an oscillation coil as indicatedin FIG. 10, it will be possible to receive shortwaves stably and easilyin the same manner as described above.

Since, especially in the case of portable radios, the tuning dials aresmall, adjustment by means of a conventional system depending solely onself-oscillation is. extremely difiicult, but this difiiculty can beeliminated by using the system of the present invention in same manneras described above.

In FIGS. 2 through 10, inclusively, the crystal oscillator X inserted atvarious circuit positions have been diagrammatically represented asbeing composed of a single crystal, but such representation has beenmerely for the purpose of illustration and is not intended ltO limit thenumber of crystals to be used. That is, two or more crystals may beconnected and used as illustrated in FIGS. 11 through 16, inclusively.

FIGS. 11 and 12 show one example of a specific construction of oneexample of embodiment of the crystal oscillator according to theinvention, wherein three crystals 1, 2 and 3 are inserted in a quartzcrystal holder of the FT 243 type. The crystals 1, 2 and 3, which have 4different frequencies, areinstalled in laminate arrangement, and thecombination. can be used similarly as an ordinary crystal oscillator.*When the internal electrostatic capacity of the crystal oscillator isto be decreased 'or increased because of such considerations as theposition in the oscillation circuit where the crystal oscillator is tobe inserted, two or more crystals can be connected in such arrangementsas series connection, parallel connection, or series parallel connectionas indicated diagrammatically in FIGS. 13 through 16, inclusively. 1

In such cases wherein two or more crystal oscillations of differentfrequencies are required, as in an oscillator for. calibrationzoffrequency of a standard signal generator or in the aforeadescribedreceiving system as applied to a superhetcrodyne receiver, the use ofthe crystal oscillator of the present invention as described above makesit possible to obtain oscillation at one required frequency selected atwill from among two or more frequencies by merely moving a variablecondenser of the tuning, circuit of the oscillator.

III the above case, conventional crystal oscillators cannot be usedunless the said crystal oscillators are interchanged, or are changedover by means of a e-witch, whereas,with the crystal oscillator of thepresent invention, such inconvenience is eliminated. Accordingly, thecrystal oscillator of the present inventionhas the advantage ofconvenience, economy, and small space requirement Since it isobviousthatchangesand modifications can r be made in the above described detailswithout departing from the nature and spirit of the invention, it is tobe understood thattheinvention is not to be limited to the detailsdescribed herein except asset forth in'the appended claim.. a a

Weclaim: V In a superheterodyne, intermediate frequency type,

radio receiving circuit, including a variable condenser tuning stage, afrequency convertor stage having a local oscillator, which circuitalsoincludes crystal oscillators,

the number of which correspond toa particular number ofireceived Waves;the improvement therein comprising having said crystal oscillatorsinclude a holder, at least two crystals having different oscillationnatural frequen-' cies, laminated and held by said holder, said crystalsbeing electrically connected by the use of two electrode plates, saidcrystal oscillators being connected to said local oscillator, thenatural oscillation frequency of each of said crystal oscillators beingmade to differ from the frequency of its particular received wave bysaid intermediate frequency, said'local oscillator stage having avariable condenser including a movable condenser part coupled to thecorresponding part of the variable condenser of the tuning stage so thatsaid local oscillator variable condenser is adjusted by the tuning ofsaid tuning stage making the resonant frequency of said local oscillatorsubstantially coincide with the natural oscillation frequency of one ofsaid crystal oscillators, thus enabling stable reception of a selectedparticular received wave, said local oscillator moreover acting as aself-oscillation circuit when radio Waves other than said particularnumber waves are received so as to provide ordinary reception.

References Cited in the file of this patent UNITED STATES PATENTS2,083,420 Atchison June 8, 1937 2,323,924 Mayer July 13, 1943 2,580,051Torre et al. Dec. 25, 1951 2,887,573 Hruska May 19, 1959 FOREIGN PATENTS655,256 Germany Jan. 12, 1938

